Is there a variable Ex in Electromagnetic Waves module?

Dear all,

By the question in the title, I mean a variable named exactly as Ex, without emw. prefix. Is it an internal variable?

I input such a variable by mistake in a model. COMSOL didn't report an error, but the results were totally wrong. After changing to emw.Ex, the results make much more sense.

Thanks!
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Pu, ZHANG
DTU Fotonik